The present invention is directd to a flow regulator which reacts to the concentration of hydrocarbons in a vapor to control the flow rate of the vapor as it passes therethrough. More specifically, the invention is directed to a concentration sensor or flow regulator which incorporates therein a material which expands or contracts in accordance with the concentration of hydrocarbons to control the rate at which gasoline vapor containing hydrocarbons may be removed from a storage or evaporation canister and returned to the intake manifold of an engine.
In order to control the emission of residual hydrocarbon vapors within the intake manifold of an engine or within the fuel tank, charcoal canisters have been incorporated within the pollution control system of internal combustion engines for storing these vapors. When the engine is restarted a control device such as a control solenoid may be used to regulate the rate of flow purge air from the canister into the intake manifold. The control solenoid or similar device is typically vacuum responsive and during idle or under light engine load, when there exists a large degree of engine vacuum, the hydrocarbons may be returned at a substantial concentration to the engine. During light engine load conditions there may be a surge in hydrocarbons in the exhaust if the canister is saturated. Typically, an open loop control is used to regulate the flow rate of canister purge air to the intake manifold which is varied with engine load and speed but not in proportion to the amount of hydrocarbons stored within the canister. Consequently, it can be seen that, as used in the prior art, if the rate is modified based only on engine load and speed without the knowledge of the degree of hydrocarbon concentration within the canister, a surge in hydrocarbons in the exhaust may occurr. In addition, since many fuel management systems are closed loop systems that incorporate an oxygen sensor in the exhaust system the surge inhydrocarbons caused by the intake of hydrocarbons from the evaporation canister could cause the engine management system to reduce the amount of fuel going to the fuel injectors of the engine which would cause the engine to misfire or otherwise run rough. One solution to obtaining information regarding the saturation of the charcoal canister or of the concentration of hydrocarbons in the vapor flowing therefrom is to incorporate within the pollution control system a sensor which monitors the concentration of hydrocarbons and thereafter generates a signal which is received by the electronic control unit within the fuel management system to modify the rate at which fuel is ingested into the engine in view of these additional hydrocarbons released into the intake manifold. Such a system, while enabling a closed loop control system to compensate for hydrocarbon flow is invariably expensive and complicated. The present invention provides for a simple and reliable solution to the above deficiencies in the art.
It is an object of the present invention to provide a concentration sensor which varies its physical characteristics in accordance with the concentration of hydrocarbons within a vapor to regulate the flow rate of the vapor accordingly. More specifically, it has been found that when silicone rubber is exposed to gasoline vapor the silicone rubber will expand in accordance with the concentration of hydrocarbons.
Accordingly, the present invention comprises: A flow regulator or sensor for restricting the flow of vapors therethrough in accordance with the concentration of hydrocarbons in the vapor. The regulator comprises a housing comprising cojoined a first and second housing members cooperating to define a chamber. The first housing member includes inlet passage means for communicating vapor thereto, and the second housing member includes outlet passage means for the vapor to flow out from the housing. The regulator further includes a body of hydrocarbon sensitive material partially filling the chamber, the material being capable of expanding and contracting in proportion to the concentration of hydrocarbons in the vapor communicated thereto. The material includes at least one flow passage, in communication with the passage means, through which the vapor may flow, support means in contact with an exposed end of the material including at least one opening therethrough in communication with the at least one flow passage, and movable with the material, a control orifice positioned within the housing, and piston means supported at one end by the support means and movable therewith and including another end cooperating with said orifice to regulate the flow area through the control orifice in proportion to the movement of the material.
Many other objects, advantages and purposes of the invention will be clear from the following detailed description of the drawings.